student summoned to his office and asks dieir opinions about school code the school should have. He telephones the parents of every tenth

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1 EXAMPLE: The principal of the new school is also interested in what type of dress code the school should have. He telephones the parents of every tenth student summoned to his office and asks dieir opinions about school dress codes. What type of study is this?

2 Planning and Conducting Surveys :Hj EXAMPLE: A journalism class prints a survey in their school newspaper. Readers are asked to clip the survey from the paper, complete it, and return it to a drop box in the school cafeteria. What type of sample is this? EXAMPLE: A journalism class stations pollsters in front of the stadium during a football game. They ask each student who enters his or her opinion of the quality of the school's athletics program. What type of sample is this?

3 EXAMPLE: A media research firm is conducting a poll on an upcoming election for city council. Trie firm obtains a list of all 15,000 registered voters in the council ward under consideration. The voters' ID numbers are entered into a computer and 500 are chosen at random, without replacement, to comprise the sample. What type of sampling design is this?.,;. EXAMPLE: A media research firm is conducting a poll on an upcoming election for city'council. The firm obtains a list ofjall 15,000 registered voters in the council ward under consideration. The voters' ID numbers and party affiliations (Democrat, Republican, Independent) are entered into a computer. The firm randomly selects, without replacement, 200 Democrats, 200 Republicans, and 100 Independents to comprise the sample. What type of sampling design is this? 3 00 U*\ 2. Pa

4 EXAMPLE: A media research firm is conducting a poll on an upcoming election for city council. The firm obtains a list of all 15,000 registered voters in the council ward under consideration. The voters' ID numbers and voting precinct numbers (01-75) are entered into a computer. The firm first randomly selects 20 of the voting precincts. Then, from each of the chosen precincts, 25 voters are chosen with simple random samples. What type of sampling design is this? <n«2.5 are. EXAMPLE: A media research firm is conducting a poll on an upcoming election for city council. The firm obtains a list of all 15,000 registered voters in the council ward under consideration. The list is sorted by voter ID number. The firm randomly selects one person from the first 100 on the list; then it selects every 100th person after that. The sample size is 150. What type of sampling design is this?

5 \Cj Bias and Sampling Error EXAMPLE: A journalism class prints a,survey in their school newspaper about the school charging students for parking. Readers are asked to clip i Kthe survey from the paper, complete it, and return it to a drop box in the school cafeteria. Why is this sample biased? UJ T"0 L A*-* /H0«.f TO SfcfoJ THe EXAMPLE: A journalism class stations. pollsters in front of the stadium during a football game. They ask each student who enters his or her opinion of the quality of the school's athletics program. Why is this sample biased? A TO 0 F, EXAMPLE: A media research firm is conducting a poll on an upcoming election for city council. The firm obtains a list of all 15,000 registered voters in the council ward under consideration and a simple random sample of 500 voters is chosen. Over a 24-hour period, telephone calls are placed to the voters, with follow-up calls made to those voters who do not answer the phone on the first attempt. Pollsters could not reach 37 of the 500 voters selected. What sources of bias could exist in this survey? o -t- 37

6 EXAMPLE: A journalism class conducts a simple random sample of students at their school. They ask each student, "Given the fact that our school has won seven championships in the last five years, do you favor or oppose reducing funding for athletic programs?" What sources of bias could exist in this survey?»s A To^n^ OF ssfowifr /»* O